After 40+ years, the disk drives need a bit of maintenance. Fisr they were removed from their mounting frame, each was identified as being the same model which makes swapping them around a lot easier.
I’ve not been able to find my old disk head cleaner so using cotton buts and IPA were used instead. Drive A appears quite dirty, so was probably the cause of the the disk read errors. I assumed that drive C would have been the least used so was swapped with drive A. The drive selection links needed to be swapped too.
The drives were replaced, machine reassembled and tested. No disk read errors were seen during initial testing.
